Techniques for using sunlight and solar heat as the renewable energy source have been developed (See, for example, Japanese Unexamined Patent Application Publication No. 2011-137620, U.S. Patent Application Publication No. 2009/0056703 A, PCT International Application Publication No. WO 2012/042888 A and NEDO Renewable Energy Technology White Paper, 2nd Edition “Chapter 5 Solar thermal power generation and usage of solar heat”). The techniques using the solar heat that have been developed include the trough type solar thermal power generation system, the Fresnel type solar thermal power generation system, the tower type solar thermal power generation system, and the dish type power generation system, and the like which are classified according to how the light is collected. In these techniques, the solar tracking type reflection mirror for increasing the efficiency of collecting the solar heat and the rate of collecting the sunlight has been introduced. The solar tracking type reflection mirror drives a reflection mirror (heat collecting mirror) in accordance with the movement of the sun.
The solar tracking type reflection mirror includes a single-axial tracking type and a dual-axial tracking type. In the single-axial tracking type, the positional relation between the sun and the reflection mirror is adjusted along one axis. For example, the angle of the reflection mirror is changed one-dimensionally along the east-west axis only or along the north-south axis only in accordance with the daily movement of the sun. In the dual-axial tracking type, the positional relation between the sun and the reflection mirror is adjusted along two axes. For example, in accordance with the daily movement of the sun, the altitude of the sun is tracked while changing the angle of the reflection mirror and the azimuth of the sun is tracked by rotating the reflection mirror. Alternatively, the azimuth and the altitude of the sun are tracked by changing the angle of the reflection mirror along both the east-west axis and the north-south axis. The dual-axial tracking type reflection mirror is capable of precise angle control in the dual-axial direction. Therefore, in general, a reflection mirror with a smaller surface area than that of the single-axial tracking type reflection mirror executing the angle control only in the single-axial direction is employed. At present, the trough type solar thermal power generation system and the Fresnel type solar thermal power generation system employ the single-axial tracking type reflection mirror. On the other hand, the tower type solar thermal power generation system and the dish type solar power generation system employ the dual-axial tracking type reflection mirror.